1. Field of the Invention
The present invention relates to a method of allocating a storage area, and particularly to a method of allocating a logical storage area.
2. Description of the Related Art
As an efficient and effective use method of the resources of a storage area, there is a disk array including plural storage devices. The disk array enhances the reliability by causing the internal storage area to have redundancy, and provides plural hosts with storage areas of required capacity as logical volumes. By this, one storage apparatus can manage the storage areas of plural hosts. Besides, the resources of the storage area can be efficiently and effectively used.
The logical volume includes plural storage areas in page units. The page means the size of a storage area obtained by dividing a storage area of a physical storage device by an arbitrary size. Hereinafter, the storage area in the page unit is simply referred to as the page. The page of the physical storage device having free capacity is allocated as the logical volume of the host, so that the capacity of the logical volume used by the host can be increased.
As a method of providing the logical volume to the host, there is a method in which the capacity of the storage area to be allocated to the host is dynamically changed according to an I/O request from the host, and the logical volume is allocated to the host (see, for example, patent document 1 (JP-A-2003-15915)).
Hitherto, allocation of pages of a logical volume provided to a host for business use is performed so that the pages are allocated so as to be dispersed (at random) in plural physical storage devices. By this, when data is read, since the data is dispersed in the plural physical storage devices, the physical data read time is reduced and the performance of the host for business use becomes high.